Indicator for alternating electric current transformers



06L 1952 s. A. STEVENS 2,6 3,

INDICATOR FOR ALTERNATING ELECTRIC CURRENT TRANSFORMERS Filed Nov. '7, 1947 Patented Oct. 7, 1952 INDICATOR FOR ALTERNATING ELECTRIC CURRENT TRANSFORMERS Sydney Arthur Stevens, London, England, as-

' signor, by mesne assignments, to Westinghouse Air Brake Company, a corporation of Pennsylvania ApplicationNovember 7, 1947, Serial No. 784,671 In Great Britain April 24, 1947 This invention relates to alternating electric current transformers, and has for its object to provide arrangements for automatically giving an indication that a transformer is under load, that, is, is supplying current to a circuit connectedjto the secondary windingof the transformer.

According to the invention, the magnetic core of .the transformer carrying the usual primary and secondary windings is provided with an additional winding so symmetrically disposed relative to the magnetic fluxes linked with the primary and secondary windings that an electromotiveforce is induced in the additional winding onlyin the event of there being any difference between these magnetic fluxes, the additional winding being connected to an electrical indication device such for example as an electric lamp. When a transformer is energized by the connection of its primary winding to a supply circuit, the secondary winding being open-circuited, the only magnetomotive force in the transformer core is that due to the primary winding, so that substantially the same flux is linked with both the; primary and secondary windings. When, however, the circuit of the secondary winding is closed,. as is the case whenthe transformer is loaded, the current in the secondary winding causes a magnetomotive force in the core which isopposed to that due to the primary winding, with the result that the flux linked with the secondary winding is no longer substantially the same as that linked with the primary winding.

As a result, the additional winding consisting of a single coil oppositelylinked with both these fluxes, or two coils each linked with one of the I fluxes and oppositely? connected together will, whenthe transformer is loaded, have induced therein an electromotive force causing a current to flow inthe additional winding to energize the lamp or other indication device.

In carrying the invention into practice, the additional winding may consistof a fiat coil surroundingboth the primary and'secondary winding core limbs, or suitably arranged on the yoke members connecting these limbs; Alternatively, anadditional coil may be provided on each of the primary and secondary winding core limbs, these coils being reversely connected in series in the circuit of an incandescent lamp constituting the indication device.

In a still further form of the invention in which the primary and secondary windings of the transformer are arranged on different limbs of the core, the latter being provided with an addi- 4 Claims. (01. 177-311) tional limb constituting a 'leakagepath for the magnetic flux,theadditional winding is constituted by a coil surroundingthe additional core limb. c

The additional winding may only comprise a relatively small number of turns, so that-a relatively low voltage lamp maybe employed.

The invention is not. limited to the particular arrangements above described by way of example as the additional winding may be arranged or disposed in any position relative to the transe former core which will enable the winding to b energized, as above described.

I shall describe three'forms' of apparatus embodying my invention, and shall then point out the novel features thereof inclaims.

In the accompanying drawings, Fig. 1 is a diagrammatic View showing one form of apparatus embodying my invention, in which an additional or leakage flux winding consisting of a singlecoil surrounds both the primary and secondary windings of a transformer; Fig. 2 is a diagrammatic view showing amodified form of the apparatus of Fig. 1, in which an additional coil is provided on each of the primary and secondary winding core legs of a transformer; and Fig. 3 is a diagrammatic view showing another modified form ofthe apparatus of Fig. l, in which an additional winding is provided on a leakage block for a transformer.

Referring first to Fig. l, a transformer T is provided with a primary winding P onone of the legs of its core I}, and with a secondary winding S on thg opposite leg of its core I. An additional or leakage flux winding L surrounds both the primary and secondary windings P and Sand core I. An indication device, shownas a lamp K, is .connected in a circuit which includes leakage flux winding L.

. Primary winding P iscbnstantly energized from ample, as the vwell-k'nownbrifdge type comprising four asymmetric units 1 '3i-and 42 which may be of the well-known copper oxide rectifier type.

With primary winding P energized, and with the circuit shown for secondary winding S closed through switch W, a magnetomotive force in transformer core I, which is caused by the ourrent in the secondary-winding S, opposes the magnetomotive force in the core which is caused by current in primary winding P. Therefore, a leakage magnetic flux is produced which links with winding L and generates electrical energy in winding L for lighting lamp K.

If thecircuit-for winding S is -opened,such as by opening switch W or by a broken'connection, or if, for any other reason, current ceases to pass from secondary winding S for charging battery Q, practically all the magnetic flux produced in core I by winding P will remainin core -I, so that there will be practically no leakage flux for energizing winding L. Lamp K will therefore be extinguished.

Referring next to Fig. 2, the form of apparatus here shown is similar to that in Fig. 1 except that, instead of winding L shown surrounding windings P and S and core I, two'other'sepa'rate additional windings, constituting the additional or leakage flux winding, designated by the reference characters IL and 2L, are shown. Winding lL isaround thev same leg ofycore. I as winding P, and winding 2L--is 1 around the same leg of core i as winding 6. Windings 1L and 2L are connected in series with each other in a circuit which includes an indicator K. Windings l-L'and 2L are also connected in this circuit in opposition to each other withfrespect' to the magnetic flux in core I due 'to current in .either winding P or S.

With winding P energized from terminals BX andNX, and with the circuit for 'windings'closed through switch W, the ma'g'netomotive force produce'd in core I by the. current in'winding S, opposes the magnetomotiveiforce produced by the current in winding P, so that the flux linked with winding 2L will not be the same as that linked with. winding IL. The electromotive force resulting from the difference in electromotive forces thus generated in windings FL and 2'L passes .current for lighting lamp K.

If the circuit for winding S :is opened, or if for any other reason current ceases to pass from secondary windings S for charging battery Q, the only magnetomotiye force in core 1 will be that 'due to winding P, and therefore the flux produced by this magnetomotive force, which links with winding 2 L, iwill be practically the same as that which links with winding IL. The electromotive force-'generated in winding 2L will therefore be practically equal and opposite to that generated in winding IL, and hence lamp K will :be extmguished.

Referring now to Fig. 3, the form ofappara tus here shown is similar to that -in-Fig. 1 except that, in'steadof winding-L shown surrounding windings P and S :and core l, a leakage block 2 is provided for 'core 1, and the additional -'or leakage winding L isplfiifle'd around leakage block 2. iii/1thwinding P energized from terminals BX and NX, and with the circuit for winding-'S'closed through switch W, the magnetomotive force in core I; due to the current in winding :S opposes that "due to the .curre'nti'n winding P, causing ieakage fiux to :pass, through leakage block 2'. Winding L is .there'iore energized, for lighting lamp K. If the circuit for winding S is opened, orwif,-,for any other-reason current ceases to pass from: secondary :winding S for charging battery Q, ractically all. the. magnetic fiuxproduced in core; I by, winding P will remain, in core I so that ther -will be practically no leakage flux through alternating electric current transformers. em-

bodying my invention,-'it-'is understood that variious changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of mgr-invention.

Having thus described my invention, what I claim is: U r Y 1. In combination, a transformer comprising a ,primary winding and a secondary winding on a core, a leakage'block for said core, a leakage flux winding surrounding said leakage block, and an indication device energized by current from said leakage flux winding only if said primary winding'is-energized and said secondary winding is in a closed circuit.

2. combination, a transformer :comprising a primary winding and a secondary winding, a leakage block for said transformer, -a leakageflux wmdingraround 'saidfleakage block, and a'ndndication device energized by current from said leakage flux winding =only if said primarywinding is energized and said secondary winding is in a-closed'circuit.

3. alternating electric current transformer comprising a primary winding and -ar-seccndary winding and also an auxiliary winding, 'said'sec ondary winding beingipositioned tolinkawith primary magnetic flux produced by current in said primary winding, and said auxiliary "winding be ing positioned to link with leakage flux from said transformer but being positioned out of linking relation with said rimary magnetic flux which is in linking relation with both said primary winding and said secondary winding in said transformer. i

4. In combination, a transformer comprising aiprimary winding an'd' a secondary winding position'edto link with primary magnetic fiuxpreduced by current in said primary winding, an auxiliary winding positioned -to-Ii'rik with leakage flux from said transformer but-being positioned out or linking relatib n with said primary ma' netic flux which is inlinkin'gr'elati0n with both said primary 'windin'g 'and said secondary wine ing in said transformer, indic ation mea s, and means 'for' energizing' said indicationmeans by current from said auxiliary winding-only if said primary winding is energized and said secondary windingis ina closedcircuit' I V SYDNEY STEVENS.

REFERENCES. 'CI IIED.

V The following references are or record in the file 'o'ffthis patent: UNITED 'STATESP-KTENISL 1 

